Nowadays optoelectronic devices including light emitting diodes (LED) are utilized as the light source in public and commercial displays, automobile lamps, building illumination, indicators and the like. As the reflector material for LED, thermoplastic resins, polyphthalamide (PPA) resins are often used. Recently, epoxy resins containing acid anhydride as the curing agent are also used as the reflector material. Meanwhile it is in a rapid progress to increase the light intensity of LED devices, which are used as the backlight unit for LC displays and the light source for general illuminations. In these applications, the LED must meet rigorous requirements of reliability and durability. Although thermoplastic resins such as PPA, liquid crystal polymers, and heat curable resins such as epoxy resins are commonly used as the reflector, they cannot be used in the environment accompanying simultaneous exposure to both heat and light, because they can be substantially degraded, discolored, and reduced in light reflectivity.
Potential use of heat curable resins such as epoxy resins and silicone resins as the LED reflector material is described in Patent Documents 1 to 6, 8 and 9. Also a matrix array of reflectors is described in Patent Document 7.
Currently, LED reflectors made of such heat curable resins are in commercial use. The wall defining a side surface of the reflector becomes thinner, with most walls being as thin as about 100 μm. In the case of reflectors made of commonly used thermoplastic resins such as PPA, and liquid crystal polymers, thinning of the side wall gives rise to no substantial problems because the resins themselves are tough.
In contrast, heat curable resins are generally brittle as compared with thermoplastic resins. Thus reflectors made of heat curable resins have the serious problem that they are prone to break by impact.